Thermotropic liquid crystalline polymers are wholly aromatic condensation polymers that have relatively rigid and linear polymer chains. When these polymers melt they orient to form a liquid crystal phase. The formulations are generally derived from aromatic hydroxy acid monomers (e.g., hydroxybenzoic acid (“HBA”) or 6-hydroxy-2-naphthenic acid (“HNA”)), either alone or in conjunction with other aromatic monomers, such as diacids (e.g., terephthalic acid (“TA”) or isophthalic acid (“IA”)) and/or dials (e.g., hydroquinone (“HQ”), acetaminophen (“APAP”), and 4,4′-biphenol (“BP”)). Liquid crystalline polymers make up a family of thermoplastics that have a unique set of properties. They perform very well in harsh environments, exhibiting high heat resistance and tolerance, high electrical resistance, and high chemical resistance. Although liquid crystalline polymers have many unique advantages, they also have shown disadvantages. For instance, the strength characteristics exhibited by liquid crystalline polymers are often not adequate for certain applications such as thin-walled portions of electrical connectors, printer parts, etc. Moreover, as the demand grows for small and light products, polymers that exhibit adequate mechanical characteristics are being sought as replacement for heavier metal materials, for instance as framing for portable electronics.
Efforts have been made to improve the physical characteristics of liquid crystalline polymers through various means including the formation of blends with other polymers, the introduction of certain fillers into the liquid crystalline polymer composition such as specific amounts of inorganic fillers, the inclusion of small molecules or oligomers into a blend, the incorporation of additional monomer units into the polymer backbone as a repeating unit, and so forth. One commonly employed method for improving physical characteristics of liquid crystalline polymers is through incorporation of a naphthenic acid chain disrupter into the polymer backbone. For instance, HNA has been incorporated into the polymer, and is generally believed to disrupt the linear nature of the polymer backbone and thereby affect characteristics of the polymer, such as melting temperature. Unfortunately, the utilization of naphthenic acid derivatives as a chain disrupter can lead to other less desirable results. For instance, reactivity of the naphthenic acids with other monomeric constituents can occur and may have unintended consequences on the final properties of the polymer composition. Moreover, high amounts of naphthenic chain disrupters can lead to a lower level of molecular orientation, which can affect mechanical properties. In addition to functional concerns, the high cost of naphthenic acids alone dictates that the need for avoidance of these materials.
As such, a need continues to exist for a thermotropic liquid crystalline polymer that exhibits desired mechanical characteristics while avoiding undesired issues as have been encountered in the past.